- Mp3 are audio files compressed using lossy compression.
- The lossy compression allows great savings in file size, with the average MP3 file being 90% smaller than an equivalent uncompressed audio file.
- Like all lossy compressed files, savings in size are made by deleting data that the computer believes is redundant and will not be missed by the user.
MP3 audio compression reduces a file size through:
- Perceptual music shaping
- Reducing the audio bitrate
Perceptual Music Shaping:
- Perceptual music shaping refers to the process of removing inaudible sounds in order to make a file size smaller.
- Inaudible sounds may include noises at frequencies that human cannot hear, quiet sounds that cannot be heard over louder sounds.
- In audio files, the bitrate is the number of bits that need to be processed every second. This is measured in kilobits per second.
- The bitrate is calculated by multiplying the sample rate by the bit depth and number of audio channels.
- The bigger the bitrate, the better the sound quality, but the larger the file size.
Sample Rate:
- The sample rate (measured in Hz or kHz) is the number of samples (snapshots in time) of sound that are recorded to represent an audio performance.
- Taking more samples per second will result in a more accurate and better sounding audio file. However, increasing the sample rate increases the file size.
Bit Depth:
- Bit depth is the number of bits of information recorded in each sample.
- MP3 with a high bit depth will contain a wider spectrum of frequencies, giving a more accurate recording of the audio performance. However, the higher the bit depth, the greater the file size.
Advantages:
- The low data size (file size) is the biggest advantage. A smaller file size enables the user to rip a large amount of music files on a disc.
- The files can be easily shared via an online medium (Internet) or a physical medium (USB, CDs).
- Time taken to download and upload files has reduced significantly. MP3s can be downloaded through HTTP or FTP sites. Earlier if a single music file download would take hours, with this technology the time is reduced to only a few minutes!
- MP3 files can be played by many types of devices such as CD players and Apple iPods. You can also play MP3 files with media players such as Winamp, Windows Media Player, or QuickTime.
Disadvantage:
- The biggest disadvantage is the low audio quality. MP3 uses a "lossy" algorithm that deletes the "lesser audible" music content in order to reduce the file size, thus compromising on the music quality.